The invention relates to a compact fail safe interface. An interface of this kind is designed to be used in a strongly fail safe system.
Some fail safe systems make use of dynamic fail safe logic techniques. A strongly fail safe frequency coding system, enabling the dimensions of such systems to be appreciably reduced, is described in European patent EP-385,885. This type of system nevertheless presents the drawback of requiring a large number of components and of imperatively requiring a periodic off-line test to ensure the strongly fail safe property.